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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Maryland CDL knowledge test. The MD CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Maryland CDL Manual. Take this MD CDL practice test now to prepare for the actual air brakes test!
1. A broken exhaust system:
does not cause problems.
can let poisonous carbon monoxide to leak into the cab.
can improve fuel efficiency.
poses no threat to the driver.
2. You must take the CDL skills tests in the type of vehicle for which you wish to be licensed. If your test vehicle does not have air brakes:
you won't receive a CDL.
you'll need to take another knowledge test about air brakes.
you'll have to immediately retake your test using another vehicle.
you will be restricted to driving vehicles without air brakes.
3. If air pressure does not build up fast enough:
you may be forced to turn off the engine and release the parking brake.
you should put the parking brake on and gently pull against it in a low gear.
you should turn the electrical power on and step on and off the brake pedal.
the pressure may drop too low during driving.
4. To use the controlled braking method in an emergency, you should:
pump the brake pedal 3 times.
apply your brakes all the way, and release the brakes when the wheels lock up.
apply the brakes as hard as you can without locking the wheels.
apply the brakes when the wheels lock up.
5. With brake drums, if brakes become too hot:
your ABS will malfunction.
the brakes may stop working.
the brakes will supply too much power to the drive wheels.
the air compressor will kick on to cool the brakes.
6. In a dual air brake system, if one air system is very low on pressure:
you should pump the brakes to restore pressure.
the effect won't be noticeable for the first 50 miles.
you should drive and brake as you always have.
either the front or rear brakes will not be operating fully.
7. With a fully-charged air system, the leakage rates should be less than:
2 psi for single vehicles and 3 psi for a combination of two vehicles.
5 psi for single vehicles and 10 psi for a combination of two vehicles.
5 psi for single vehicles and 4 psi for a combination of two vehicles.
3 psi for single vehicles and 4 psi for a combination of two vehicles.
8. The tractor protection valve:
will close automatically if the air pressure drops to a certain level.
provides the air supply for the brake system.
will close if you apply the parking brakes.
All of the above.
9. Emergency brakes are:
not required on doubles.
not required on commercial vehicles with air brakes.
not required on buses.
required on all vehicles.
10. If an aggressive driver is involved in an accident down the road, you should:
make eye contact with the driver.
try to get their vehicle to the side of the road.
confront the aggressive driver.
stop a safe distance from the accident scene, wait for the police and report the behavior you witnessed.
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MD CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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